Compositions and methods for making the same



. streams.

UnitedStates Patent COMPOSITIONS AND METHODS FOR MAKING THE SAME Roger W. Strassburg, Cleveland, Ohio, assignor to The B. F. Goodrich Company, New York, N. Y., a corporation of New York No Drawing. Application December 22, 1955 Serial No. 554,614

23 Claims. (Cl. 106-288) This invention relates to novel inorganic silicon and oxygen containing pigments. More specifically, this invention relates to fibrous inorganic compositions of silicon and oxygen which are especially useful as intermediates for making reinforcing pigments for elastomers and to methods for making the same.

Monox or solid, particulate, disproportionated silicon monoxide (SiO .(Si) where x and y are integers, is produced by the reaction of carbon and silica at high temperatures under reducing conditions, such as in an arc furnace, and allowing the gaseous reaction products containing SiO to condense in a partial or in an essentially complete vacum or vacuum chamber or in an inert atmosphere or gas of nitrogen, argon, helium, CO, etc. In place of carbon, silicon or silicon carbide can be used to produce SiO gas. Alternatively, silicon metal can carefully be oxidized to SiO gas which then can be condensed. Still other methods for making Monox can be used.

Monox is characterized as being solid, finely-divided or particulate and exhibiting under the electron microscope a mixture of fibrous particles and non-fibrous and possibly spherical particles. If the process is conducted in a manner that the inert condensing gas and the silicon monoxide gas stream mix together with little or no turbulence, especially long and tendrilous fibers are obtained. Moreover, the amount of the non-fibrous particles is materially reduced and is less than the fibrous particles. In such process the inert condensing gas also should be essentially pure, that is, it should contain only a few parts of an oxidizing gas per million parts of condensing gas, or if it is of a commercial variety containing a minor amount of oxygen or oxidizing gases, it should also contain a minor amount of an amine such as ammonia, ethyl amine and the like or a hydrogenfurnishing gas such as hydrogen, methane, ethane, etc. to remove any traces of oxidizing gas in the inert condensing gas as well as in the furnace gases. If desired, generally non-fibrous Monox can be obtained by merely blowing the silicon monoxide gas stream from the furnace with any of the above inert condensing gases, or gas mixtures, to cause turbulence in' the mixing gas The Monox may contain minor amounts of nitrogen, usually about 1-8% by weight of bound nitrogen probably as (SiONH);, x being an integer, i. e.,

H S:l--l IS;i in which nitrogen is attached to two silicon atoms, so that part of the Si is tied up if the inert condensing gas was nitrogen and if it also contained from about 0.5 to 9% by volume of a gaseous amine. However, very little (less than 1% by weight) or no nitrogen is present in Monox if a pure inert condensing gas is used or a commercial variety of inert gas containinga hydrogen furnishing gas is used and. the silica and carbon used are very pure. The latter described Monoxefiect s a v 2,865,778 Patented Dec. 23, i958 less rapid cure in rubber containing compositions due to its greater acidity.

In general, the fibers of the fibrous type of Monox have a ratio of length to width of from about 10:1 to 50:1 or greater and exhibit a surface area of from about 60 to 200 square meters per gram although the surface area may be smaller or larger. Their average length will vary from about 50 to 600 millimicrons or higher. The non-fibrous particles, if any, in the mixture may have an average particle size of from about 5 to 200 mu and a surface area of from about 200 to 300 square meters per gram. When the SiO gas is blown with an inert gas, the generally non-fibrous particles obtained have a random range of particle sizes of from about 5 to 200 mu and a surface area of from about 200 to 300 m. /g.

It has been found that Monox, particularly where the fibers are in a major amount and very long and the ratio of the length to the width of the fibers is high, is useful as a. reinforcing pigment for various elastomeric products such as rubber, vinyls, polyesterurethanes, silicones, and the like. However, Monox is brown, and, accordingly, the color of the products produced with it are brown. This color can not be masked by the use of color pigments without materially destroying the reinforcing properties imparted by the Monox.

It, thus, would be highly desirable to provide a method for producing a Monox type pigment, especially in the fibrous form, which is light to white in color so that when compounded with elastomeric compositions it would produce light colored to white products, would not adversely affect the color of the elastomer itself, and could be compounded with relatively minor amounts of pigments, dyes, etc., to provide useful, reinforced, colored, elastomeric products. Accordingly, it is a primary object of the present invention to provide a method for making a light colored to white, solid, particulate composition from disproportionated silicon monoxide.

It is another object of this invention to provide a light colored to white, solid particulate composition obtained from disproportionated silicon monoxide.

Another object is to provide a method for producing a composition from disproportionated silicon monoxide which is white, solid, particulate and substantially fibrous.

Yet another object is to provide a composition of matter from disproportionated silicon monoxide which is white,'solid, particulate and substantially fibrous and is useful as a reinforcing pigment for elastomers.

These and other objects and advantages of the present invention will become more apparent to those skilled in the art from the following detailed description and examples.

According to the present invention, it'has been dis covered that brown Monox" prepared according to any one of the foregoing methods, can be converted into a light colored to white pigment by heating the Monox in the presence of the halogen gas at elevated temperatures below the temperature at which the Monox would tend to sinter or fuse. It also has been found that the halogen-containing gas can contain up to below about 66% by volume of an oxidizing gas, based on the total volume of the halogen and oxidizing gases, to reduce materially the silicon halides, especially silicon tetrahalides, produced during halogenation with retention of the original fibrous structure exhibited by the brown Monox. Subsequent to treatment with halogen or halogen-oxidizing gas, the resulting product may be further treated with steam or water to remove essentially all of the halogen adsorbed on or bound to the surfaces of the particles of the treated Monoxwithout adversely affect- I ing thenow light to white color of or the physical struc;

asepms ture exhibited by the new pigment. The products produced by the methods of the present invention are'essentially, particulate, solid, amorphous silicas, are fibrous and/ or non-fibrous and may ormay not contain minor amounts of halogen, hydroxyl and/or*nitrogen'groups.

During the reaction, the.halogen apparently reacts with the silicon metal of the solid, disproportionated silicon monoxide to remove it asa'silic'onha'lide, such as silicon tetrahalide, which'can be'subseguently *condensed' or J recovered and used as" a starting material 'for making various silicon-containing"products. Another byproduct can be hexahalodisiloxane. The removal of the silicon'by halogen does notfaffect thefibrous structure of the "original Monox particles "which" apparently retain their original shape, "lengthi'and particle size although some small voidsmayappear in'the fibers. Some of the bound nitrogen originally presentin"the'starting Monox may still bepresent inthe halogenated Monox. Insome cases an increase is observed in the 'surface area of the particulate material as compared to the surface area ofthe original brown Monox.

"When "an oxidizing gas is used'as a diluent for the halogengas in. an amount'below about amaximum of 66% 'by volume of .the total volume of the halogen and oxidizing'gases, it has been found that removal of the silicon metal still 'occurs'but'toa somewhat lesser de gree. At the same time,a portion ofthe silicon 'is oxidized to-silica. The product produced;depending'on the amount of oxidizing gas used, is 'still' light colored .to white. ,However, the. light'coloredproducts canbe made almost pure white by a subsequent treatment with only halogen gas. Theme of an oxidizinggas' with the halogen 'gasisdesirable sometimes in order toreduce the amount of siliconhalides obtained which maytend to presentstorage and disposal problems. It, therefore, 'isa way 'inwhich'the' ratio of the new White-pigment to silicon -halides produced can be adjusted depending "on product needs' and uses.

Subsequent treatment of the halogenatedorh'alogen- 'ated oxidized, Monox with steam serves to remove all or essentially alliof the halogen contained in the new pigment without detracting from the color' or physical structure of.-said pigment. Elastomers containingthe steam-treated, halogenated tor halogenated-oxidized Monox are just as'satisfactorily reinforced as when the original, untreated'Monox is used except that they are light'or'white in'color, or'their original-color'hasnot been materially 'afiectedyrather than being brown in color as would be the situation if untreated brown Monox was used. It is generally necessary to remove from the pigment all or essentially" all "of the halogen introduced in the halogenation step to obtain optimum physical properties in the elastomers such as the hydrocarbon rubbers and plasticized'vinylswith which the pigment may be compounded. "However;the halogenate'd or halogenated-oxidized Monox materials Will ,also ifin'd many uses as intermediates in making reinforcing pigments for elastomeric compositions-gas set-forth more particularly in copending applications of'Roger WPStrassburg filedof even date, Serial Nos; 554,648 and 554,640, entitled Methods .and Compositions of Matter and Compositions and Methods, respectively.

The halogen gas orhalogen-oxidizingpgastreated solid Monox product contains a residualgajmount;usuallyup to .about 3%, by weight'of" halogen "which'canbe'gremoved entirely or almost "entirely'by treatment-with steam at elevated temperatures. By removingentirely or almost entirely allof thehalogen means 'that insufficient halogen remains in the steamed-product to produce anoticeable effect in materials with which the product is compounded or is present in such an amount it'may be merely considered an adventitious impurity. 'It' 'is'not precisely known how the halogen is'bound to 'the pa-rticles of the new; pigment. It is believed that it-maybe attached or chemically bound to the surface of--thei par- 1: andgtemperatures are proper. :flae z.:hal ogenation step, t.the': halogenation-oxidation step,

ticles by splitting Si--Si bonds in areas of lattice im- 'perfections" and/ or by the reaction'of SiCl; with'residual OH groups sometimes found on silica materials. It may be that the halogen is both adsorbed and bound. Treatment with steam serves to hydrolyze the halogen contained in the new pigment and-to liberate it as hydrogen halide. Forexatnple, the minor amount of halogen containedin'the Monox after treatment can be represented by the following formula:

:number ofhalogen: groups The. silica containing the minor amount of halogen-in ,the lattice. can also be represented: by the following foror (SiO Hal) x where x is an integer. Two or. three halo- .g'en "atoms-may' be' attached toarsilicon atom. Halogen atoms maybe onadjacent silicon atoms. When treated witlrsteaman'd the likefthe halogen ra'dical will. hereplaced with an OH radical to givethe -following"structure:

-- --Nearby QH groups mayaalso condense if the conditions Ihepigments attthe' end of and/or the:..steaming step are..light.=colored towhite. A

"feature: of the-method ofQthe' present invention is that the halogenationprocessserves to remove any traces of-metal' lie or other ionsiwhich were contained-in the silicon monoxide gasas impurities from the carbon and other source of silicon monoxide igas andwhichmay-eondense with the SiO gas also to affect adversely the purity and color of the Monox and the new pigment.

The halogen gas used -can'..be;1chlorine, fluorine, bromine or iodine gas or mixturesthereof. It is much preferred to zusegchlorinezbecause it is more economical to use'than the :other'halogens, ii iSi not as reactive 'asfluorine' and it does =haveas higha molecular iweightias iodine. The halogen is'employed in an' amount sufficient to react with the silicon contained -in"'the original 'brown Monox. Thus, in in'g'eneral, -at"lea'st'2' mols ofhalogen are required forl g. atom'of silicon' althoughan excess is preferably employed to ins'ure compl'ete rea'ction and to' remove any' tr'aces of impurities. I

The oxidizing gas used with the halogen gas to control the amount of silicon-halides produced can be oxygen, water vapor, air or any other oxidizing gas which will oxidize at least part of the silicon in the Monox without adversely affecting its properties such as structure and surface area and will serve to control the amount of sili-.

con-halides produced. It is much preferred to use oxygen since the silicon halide vapor is not thereby diluted to such an extent that it is diificult to condense. For example, when using a. material such as air containing a large amount of nitrogen, the silicon halide vapor is so diluted with nitrogen that it is diflicult to condense and recover. It is noteworthy that the use of an oxidizing gas up to the amounts indicated below will serve to increase the yield (weight) of pigment obtained without changing the fibrous structure exhibited by the oniginal Monox while decreasing the yield of silicon halides, especially silicon tetrahalide. The pigment will also contain some halogen but in a lesser amount than when halogen gas alone was used. When using the oxidizing gas with the halogen-containing gas, they are preferably mixed together in a volume ratio below about 2:1 or, in other Words, the volume of oxidizing gas, exclusive of inert gas such as nitrogen when for example air is used, should be less than 66% of the total volume of the halogen and oxidizing gases. Preferably the volume of oxidizing gas should not exceed 50% of the total. At or above 66% of oxidizing gas, a reduction in the total amount of fibers and a shortening of the length of the fibers of the resulting pigment occurs due to melting and/or sintering such that a large proportion becomes non-fibrous and/or spherical in shape. It is not desired to obtain non-fibrous or spherical particles since they reduce the reinforcing ability of the resulting pigment in elastomeric products such as rubber. Moreover, as the amount of the oxidizing gas with respect to the halogen gas is increased above a ratio of 2: 1, the color of the pigment becomes tan probably due to a surface oxidation of the silicon metal Without a complete oxidation to the core of the silicon metal particle. This tan color, however, can be removed by subsequent treatment with halogen gas at the temperatures indicated herein so long as the color has not become locked in by fusing a layer of silica over a silicon particle or surface. A feature of the method of the present invention is that the original brown Monox need not be freshly. prepared before treatment with halogen gas. It can be permitted to stand in air at room temperature where some of the silicon is oxidized to form a film of silica over the surface of the silicon particles. So long as the film has not been produced at or subjected to high temperatures to cause fusion, subsequent halogenation will remove the remaining silicon metal. However, if the oxide film has been fused, halogen gas or the halogen-oxidizing gas mixture cannot penetrate the fused silica layer'to remove the silicon and provide a light colored to white product.

The use of steam is much preferred to the use of water, hot or cold, to remove halogen since the reaction with steam is conducted in the vapor phase and the resulting pigment is more readily handled and more easily dispersed in elastomers than one treated with water. Treatment of the halogenated product with steam to remove halogen may proceed at elevated temperature for a period of time and in an amount sufiicient to remove all or essentially all of the halogen contained in the products, although, in general, temperatures for steam treatment may be lower than those required for halogenation since the halogen is readily removed. It has been found that a relatively short treatment time, usually not more than from about 2 to 3 hours, where the original halogenation required from 50 to 80 minutes, will remove the residual halogen. Moreover, if the original Monox contained bound nitrogen, some of the nitrogen is probably removed by the steam 'with'the' halogen'but additional" steam will be required to remove all or essentially all of this bound nitrogen so that only traces, if any, of bound nitrogen remain in the product after analysis and do not materially affect the properties of the resulting steamed product when compounded in elastomers or otherwise employed. This bound nitrogen will be released in the form of ammonia. It is not absolutely necessary to remove all of the nitrogen. If desired, only a substantial amount need be removed. A product containing the same can be used for many purposes and in some instances the presence of nitrogen is of particular advantage since the nitrogen confers some alkalinity on the product so that it is not as acid as a product containing no nitrogen, for example, a product derived from Monox made in a pure inert gas or in a somewhat impure inert condensing gas containing hydrogen.

In the process of halogenating the Mono-x, it can be placed in a tube in an amount sufiicient to fill the tube without interfering with the passage of the halogen containing gas and then treated with said gas at a temperature of at least about 600 C. Since the reaction with halogen is exothermic, the temperature of the reaction should not be allowed to reach the fusion temperature of the Monox and preferably 'should not go above about 1100" C. to avoid fusing or sintering of the particles of the Monox. While the melting point of silica varies from, about 1470 to 1710 C. and of silicon is about 1420 C., the fusion or softening point of the Monox particles or new pigment will be somewhat less due to their high surface area and small particle size. However, their precise fusion or sintering point is not determinable readily with precision and, accordingly, it is preferred that the reaction temperature should not exceed about 1100" C. at which temperature appreciable fusion or sintering does not occur. Although the silicon halide gas produced during the reaction serves to dilute the halogen and to cool it and the Monox or the product somewhat during the reaction, it .still may be necessary to externally cool the tube or other reaction chamber to maintain the temperature below about 1100 C. Alternatively, cooling may be efiected by reducing the volume or amount of halogen gas to reduce the rate of reaction, or by diluting the halogen gas with a cool inert gas such as nitrogen. On the other hand, the minimum temperature required to obtain improvement in color should be about 600 C. Below 600 C. no perceptible change in the brown color of the Monox is observed. Preferably, the operating temperature should be from about 700 to 900 C. in which range a white colored pigment is produced under the best operating and economic conditions. The silicon tetrahalide produced can be collected in an ice-cooled receiver or by other means during the run and used in further processes of making silicon-containing compounds which are well known in the art.

In place of using a single tube in a batch-type process, the Monox may. be continuously treated in an inclined rotary kiln wherein the Monox is introduced at the upper end of the kiln and proceeds gradually downward while the halogen gas is introduced at the opposite end of the kiln and passes up through the kiln to react with the Monox. Alternatively, the Monox and halogen gas can pass concurrently through the kiln. Processes using fluidized beds can also be employed. Such processes are continuous and thereby contribute to the economy of the operation. Still other apparatus and techniques can be employed. It will be appreciated that such apparatus should be suitably protected to prevent contamination or corrosion from the halogen used and should contain suitable means to prevent leakage of such gas which might be hazardous.

When an oxidizing gas is used with the halogen gas, it

will be employed in the amounts indicated above and using halogen alone. Subsequentto the treatment-with;

treatment will vary according .to the size of the apparatus employed, the amount of pigment: involved, degree of agitationand the reaction temperatures produced, being careful to avoida condition-where the reaction or treating temperatures are ashigh as, the .fusion point of the Monox or the silicon dioxide containing compound being treated.

As; pointed out hereinaboveQ the halogencontaining compounds of the present invention can be used as starting materials or intermediates inother processes to provide surface coatedtpigments, useful ,as, reinforcing agents in elastomeric compounds or canbeutreatedwith a material .such as steamtoremovethe halogen contained therein and used directly in elastomeric-materials. Ad-.

ditionally, the halogen-free light colored to white pigment can be coated with various materials such as alcohols, amines, silicone resins and the like to change the surface condition of the pigment before it is incorporatedinto the elastomer. While this invention has been described with particularv reference to treatment of the brown fibrous or substantially fibrous forms of Monox which ofier the greatest improvement; in elastomeric products, particularlyrubber, it isapparent that the above remarks will apply tothe brown non fibrousorsnbstantially spherical formsofMonox which reinforce to a lesser degree but which are still usefulas arcinforcing pigment and can also be usedtas aloading material, filler and so fo-rth in variouselastomers. Moreover, the light colored to white halogen-free pigmentsprepared-by the method of the. present invention will alsov find utility in other organic compositions such as-inthermoplastics and thermosetting plastics, in hard rubbers, in rigid vinyls, in resins, in ce-' ramic compositions, in insulating compositions,; in lubri-,

ntste ct The pigments of the present invention are particularly useful in IeinfoIcing elastomeric materials. Examples of elastomeric materials which .can be used with these pigments are natural and synthetic vulcanizablezrubberssuchas natural rubber, whichis essentially a polymer of isoprene, balata, gutta percha, polychloroprene and the rub bery polymers of open-chain conjugated dienes, dienes especially having from 4to 8 carbon atoms suehas butadiene-1,3, isoprene, 2-3 dirnethyl butadiene-.l,3 and the like, or the rubbery copolymers, terpolymers and the like of these and similar conjugated dienes with each other r vwith at east e -p e abl m nomeri t r a such as isobutylene, styrene, acrylonitrile, methyl acrylate,

chloride, vinyl chloride-vinyl acetate, isobutylene, and so forth. Moreover, there can be used polymers having curable acid groups and formed by the polymerization of z major amount of an open-chain aliphatic conjugated diene and an olefinically unsaturated carboxylie acid, by he re ct o o ql metr ad ene t ,a. bqr sup: entrapment-prefe y. rrqsen epta setal tt bit copolymerization; of; a diene with an olefinically unsaturated copolymerizable compound hydrolyzable to form an; acid group, bycopolymerization of an alkyl ester-of an acrylic type acid with tan olefinically unsaturated carboxylic acid, by hydrolysis of an alkyl ester of acrylic acid 7 or by copolymerizationof-a major amount of a monoolefin orisoolefin with-a copolymerizable compound hydrolyz able .to form-groupscontaining bound --COOH. Still other polymers can beemployed such as those formed by 1 the copolymerization of dienes withalkyl acrylates, by the polymerization of alkyl acrylates alone and by the polymerization of analkyl acrylate-with at least one other olefinicallyv unsaturated monomer, which then are hydrolyzed to obtain curable. -COOH groups. In place of polymers having -COOH groups, polymers having groups such as CQOR COCI, CN, CONI-[ COONl-I and COOMe, where Meis-a metal, and the like and which are convertible to COOH-groups by ammonolysis, hydrol ysis, or similar reaetiorl fon example, by treating such polymers with dilute mineral acids, HCl or H 50 or concentrated or .,-pr eferablyvdilute KOH or NaOH, canv also be employed after such groups have been converted to a curable COOH' group Polymers having S0 11, SO H or PO H groups, or other acid groups, or deriva-.

tivesthereof convertible to the free acid on hydrolysis and which likewise can be ,cross-.linked, cured or vulcanizedcanalso be used. Polymeric vulcanizable syn-v thetic rubbers formed by. the vpolymerization of an acrylic,

acid ester, for,example,ethylaerylate or butyl acrylate, or mixturesof acrylie aeidesters or by the copolymerization of an;acrylic acid ester with a chlorine-containing monomer sueh as a minor amount; of chloroethyl vinyl, ether, vinyl chloride, ordichloro difluoro ethylene orwith, acrylonitrile, ethylene or styrene can-likewise be used, Polyester urethanes, can also be usefully employed;.they., areformed by the-reaction ofan organic diisocyanatel compound with,a hydroxyl containingv polyester reaction, product ofa,dib asic acidi and a glycol and cross linked,

cured or vulcanized ,byrmeansofga poly-functionalv hydroxyl ol hy rqxy m11 -v h silicone ubbers: a y spr eem oy g M t re ofihe or g lse omes-ca o: e p q ed- Elastomeric ma r a. other than those-specifically mentioned above are also,

useful.

In reinforcingelastomericmaterials, a minor amount of thetreatedhalogen-free pigment of the present inven tion is used with, a major amount of the elastomeric ma;

terial. Preferably, inorder to obtain the best results an. elastomeriecompositionwill, contain from about 25 to. 45% by weightofthe pigment of this invention, to from,v about to 55%, by weight of the elastomer exclusivet of other compounding ingredients.

fungicides, andso forth may beernployed with the elastomeric compositions.

For the-purposesofi thepresent invention it isto be understood that the.word; curing in the specification.

andclaims is intended to cover vulcanizing, CIOSS-rllflklllg, condensing, fusing or other treatment of the .elastomer by hi h het e t rwniusated i e v r ennre hane: arb xylfio ta ni a; p mer. ry a t, n l, other.

elastomer ororganic polymer, is converted, under ;the action ofheanlight, or vnlcanizing, cross-linking com densingand/ or other agent, into a useful material as is Curing? is;

well known, to those. skilled in the art. also intended to cover the method of only heating those, elastomers which soften on heating andharden or toughen on coolingas well as the method employing elastomers i h ni e r szl a s. ta e gemt e eremre and below Thesgreduatsi iene otiat 10 400 C. and at 500 C. In each instance no change in color of the Monox occurred. The runs were repeated at 600, 700 and 800 C. It then was noted that at 600 C. a light gray product was produced, the reaction zone to white solid silicon monoxide derivative. It is noteslowly moving down the tube as indicated by the proworthy that the use of the pigment treated as described gressively growing section of white pigment in the reacherein to remove halogen and particularly in the form tion tube. The light gray product may still be useful of fibers with or without bound nitrogen, not only affords where a white product is not' absolutely required. At good reinforcing properties to rubbery materials com- 700 C. and at 800 C. the samples were white and parable to those imparted by carbon black compounds colored bands appeared on the exit end of the reaction but'also permits the obtainment of light colored to white tube which were water soluble and were found to contain elastomeric materials. Moreover, since the pigment obferric, sodium and ammonium chlorides on analysis. The tained according to the present invention has little coveriron, sodium and ammonium apparently had been coning power, elastomeric compositions reinforced with such tained in the original brown Monox as impurities and pigment can be pigmented or dyed to provide colored had sublimed as chlorides during the reaction. Similar elastomeric materials which are not obtainable with runs were conducted in which the temperature was alcarbon black nor to any degree with the original brown lowed to run up to 1100. The resulting products were Monox. Since the pigment of the present invention has still white. All of the products from' about 600 to the same index of refraction as benzene, for it disappears 1100 were light colored to white in color and showed in benzene when added thereto, or as the elastomeric 2 no change in the length or size of the fibrous particles material in which incorporated, it does not tend to adof the original Monox although their surface area had versely color the elastomer as would the original brown been increased in some instances as shown by nitrogen Monox or an opaque pigment such as carbon black or absorption probably due to removal of some of the non to color the elastomer without reinforcing it as does fibrous particles or silicon in the fibrous particles. At titanium dioxide. Rather, the pigments produced by the well above 1100 C. sintering and melting of the parmethods disclosed herein are somewhat translucent and ticles occurred with reduction in the length of the fibers accordingly can be combined with various organic and and a reduction in size although the product obtained inorganic color pigmentssuch as phthalocyanine blue, was white. X-ray diffraction patterns of the samples phthalocyanine green, chrome red, chrome yellow, titreated within the effective operating temperature range tanium d;oxide, ultramarine blue, and the like in minor showed that the silicon ring exhibited in the pattern given amounts to givecolored reinforced elastomeric products by the starting Monox was missing. The light colored of great utility. It is only'necessary to use a very minor to white products as prepared herein contained about amount of the coloring pigment so that the reinforcing 3% of chlorine and the balance essentially SiO During properties of the present pigment are not lost. 7 the runs at temperatures of fromabout 600 to 1100 C., The following examples will serve to illustrate the crude silicon tetrachloride condensed in the ice cooled invention with more particularity to those skilled in the receiver on the exit end of the reaction tube. When art: distilled, the crude product was shown to contain about EXAMPLE I 89% silicon tetrachloride, about 2.2% hexachlorodisilox- Brown, substantially fibrous Monox was prepared by 40 ane and the balance a residue of mixed silicon halides. the reaction of anthracite coal and sand in an arc furnace to produce SiO gas which was condensed without ap- EXAMPLE II preciable turbulence using commercial (oil pump) nitro- This example was similar to Example-I, above, except gen gas containing about 1% by volume of ammonia. that the SiO gas was condensed in a mixture of com- The Monox contained about 4.07% nitrogen and 0.07% mercial nitrogen gas and hydrogen gas, the reaction tem- C l, as an impurity from the reactants, condensing gases, perature was maintained at 800 C. and oxygen gas in laboratory atmosphere, etc. A 30 gram sample of this various amounts was mixed with the chlorine gas prior brown, substantially fibrous Monox Was placed in a to treating the starting brown Monox which contained Vycor, high (90-92%) silica glass, tube having means 0.22% nitrogen, probably as an impurity from the furto heat and cool the same. The inlet end of the tube nace reactants or gases. The mixture of chlorine and was connected to a suitable source of chlorine gas while oxygen gases was passed through the Monox having a the exit end was connected to an ice-cooled receiver for surface area of 100 m. g. over a period of from about condensation of silicon tetrachloride. The tube was 100-160 minutes. The amounts of the reactants used, heated and 33 g. of chlorine gas was introduced into it the products obtained and the properties of the products and passed through the Monox at a temperature of 300 obtained are shown in Table A below:

T ableA Volume Product; 1

Ratio Monox, Product, Surface Ch, g. Crude Product, Color of PhysicalStructureofProd- Sample g. g. Aret, Added SiCli,g. Percent Product uct, as compared to mfl/g. Obtained 01 Starting Monox Oz C12 0 4 s1 20 114 46 49.5 2.11 White No Change. 1 2 29 28 11s as 32.0 0.82 do Do. 1 1 31 35 84 20 17.1 0.71 Slightly off Do. 2 1 30 36 73 30 2.9 0.33 T$1 31 f Increase in non-fibrous particles, rounding 0! ends of fibers. 14 2 0 31 37 86 do Manynon-fibrouspartlcles, sintering, fibers forming globules.

C. over a period of 50-80 minutes. No change in color of the Monox occurred and no condensate appeared in the ice-cooled receiver. Additional runs with similar Electron micrographs showed no change in structure until the ratios of oxygen to chlorine became 2:1. With the higher ratios of oxygen, the ends of the individual fibers amounts of chloride were made with the temperature at '15 became non fibrous and/or spherical because of melting,

As them/gen: ontent of, e a t ncr as {to where .oxygen alone was-used in which case the color was.locked in.

a ratioof-abOut 2:1, with production ofa light colored towhite product having essentially the same physical form as the original or-starting Monox and with a reduction ing'the amountof crude silicon tetrachloride produced: These products also contained'about 1-2 percent of chlorine Moreover as the ratio of "oxygen to chlorine becomes 2: 1' or' greater, or. oxygen alone is used, si nt eri'r 1g offthe particles of M'onox occurs in the times indicated. The. sinter-ing is probably due tothe factthat, in. the presence ofoxygen-or highconcentrations of oxygen, the, surfacesof thesilicon particles are in a very active state or'at a higher temperature than the temperatureofthe mass which facilitates sintering, fusion or agglomerationof the particles because itis noted that, when chlorine is usedsalone or oxygen is used with chlorine'in: a volumeratio oflup to. below 2:1, no visible. evidence of sintering occurs at 800C. or even up to 1100 C. Accordingly, it is apparent that oxygen should not be mixed in large amounts withthechlorine if sintering is to be avoided.

EXAMPLE III The-pigment obtained from Monox chlorinated at 700-800 C. according to Example I, above, was treated. for about one hour with steam at'a temperature above 100 C. in the tube described in Example I and'which wasata temperature of about 800 C. Hydrogen chloride was given. oif: After completion of the run the product was analyzed. The analysis showed that it still contained some nitrogen, as was present in the starting material, and also contained 0.07% by weight of chlorine showingthatall of the chlorine introduced by chlorination had been removed.- Subsequent treatment for an hour with steam underthe same conditions resulted in the removal of some of the nitrogen as ammonia. This product was also analyzed and'shown to contain 005% by weight of chlorine and 2.38% by weight ofnitrogen. Both productshad the samefibrous structure and particle size. of the startingnbrown;Monox and white chlorinated Monox of ExarnpleI and were white in color.

EXAMPLEJV.

Two samples of brown substantially fibrousMonox were halogenated at 700-800" C. and then treated-with steam according to the methods of Examples I and IlI, above, to obtain a white product. One (A) was analyzed and shownto contain 238% by weight of nitrogen and 0.05% chlorine and the other (B) was analyzed and found to contain 0.26% by weight of chlorine and 3.61% nitrogen. 60 parts by weight of each pigment were then compounded with, 100 partsof naturalrubber, 0.5 part dianilino methane, and 0.2 part sulfur on a rubbery mill at3 "-F for 15 minutes Thebatches were then cooled to 160 F;. and mill mixed with 5 parts zinc oxide, l parts .stearic acid, 1 part pine oil, 1 part phenyl beta naphthylamine, l /z'parts didodecyl amine, 1 part benzo thiazyldisulfide and 3 parts sulfur. After compounding, separate batches of thecompositions were cured at 280 F; for varying periods of-time to form-light colored vulcanizates-rand then-tested Theresults on test-are;

This. 1 example, illustrates the fact 1 that oxygencan be mixed withthe chlorine: gasup to, below- Table B' Composition containing Composition containing Pigment A. Pigment B.

Tensile Elonga- Tensile Elonga- Cure, Strength, tion at Cure, Strength, tion at Mins. p. s. i. break, Mins. p. s. i. break, percent percent These results show; thatrubber can be reinforced with;

thepigmentsof thepresent invention to-providecompm.

, sitions exhibiting useful. physical properties,

EXAMPLE V 40partsby weight ofa chlorinated andthen-steamed;

white substantially fibrous product from Monoxtdesig nated: A-;1)- prepared by the methodsof Examplesl and III, above, containing about 4% by weight'of N and 0.07% Cl, were compounded in a typical rigid vinyl formulation-comprising 100 parts by Weight of polyvinyl; chloride, andrninor amounts of lead stearate, a toughener, a stabilizer and a processing aid.

A similar fibrous white Monox (B-l) which had been,:

condensed inaninert condensing gas containing hydrogenv and wastreated withclilorine and then steam at 800C, by the methods shown inExamples I and III, above,;was, also compounded in a similar rigid vinyl formulation;

These compositions were thencompared with. a rigid;

vinyl formulation containing hydrated precipitated silica C 1). The results on; testing the compositions; are h wn mI C bs Table C Pigment, Izod. 1 Ti, C. T1.*-'C.

' containing precipitated silica. The impact resistances of nated at 700800 C. and then. treated with steam acvinyl compositions containing the products of the method of the present invention were almost twice as great as that exhibited by a vinyl formulation containing only precipitated silica; This example, thus, shows that the pigments produced by the method of the present invention can be employed in vinyl compositions to produce useful light colored products or products which can be colored with color pigments.

EXAMPLE VI Substantially fibrous brown solid silicon monoxide, Monox, preparedby condensing SiO. gaswithout appreciable turbulence in an atmosphere of commercial nitrogen gas containing a minor amount of hydrogen gas was chloricording to the methods of Examples l and lll. It was analyzed and found to contain nonreasurable amount ofi l ne e C -'Q t. ny. tr en was was.

.it'was present only as a trace. The resulting-whitefibr'ous 13 product was then formulated and tested in .a silicone rubber composition as follows:

Component: Parts by weight Above steam stripped chlorinated Monox a 40 Methyl silicone rubber (Linde Air Products Co.,

silicone gum stock X-95) 100 Dicumyl peroxide I 2 Stress strain at R. T.; cure 15' 300 F., press; 24

hrs. 300 F. oven:

This example illustrates that the pigment produced by the method of the present invention can be usefully employed in silicone rubber compositions to make light colored products.

In summary, the present invention teaches that light colored to white silicon and oxygen containing fibrous and/ or nonfibrous materials may be obtained by the treatment of brown Monox with halogen gas in a certain elevated temperature range to remove the Si in the Monox .as a silicon halide. The resulting product exhibits the same structure as the starting material and may have a higher surface area. It is useful as an intermediate in preparing pigments for reinforcing elastomers. The small amount of halogen obtained in such product can readily be removed by subsequent treatment with steam to produce products directly useful as a reinforcing pigment. Moreover, the treatment with halogen can be controlled by employing oxygen to reduce the amount of silicon halide obtained While still giving a light colored to white product having an increased silica content and the same physical form. The product produced by the method of the present invention will have great utility as a pigment which not only reinforces elastomeric materials but also permits the obtainment of light to white and even variously colored elastomeric materials.

What is claimed is:

1. The method which comprises treating a brown, particulate, disproportionated solid selected from the group consisting of silicon monoxide and silicon monoxide containing from about 1 to 8% by weight of bound nitrogen at a temperature of from about 600 C. to below the fusion point of said solid with a halogen gas in an amount suflicient to react with at least a portion of the silicon in said solid to form gaseous silicon halides and to leave a light colored to white, solid, particulate, silicon diox de composition containing halogen in an amount not in excess of about 3% by weight.

2. The method according to claim 1 in which said halogen is chlorine.

3. The method according to claim 1 containing the additional step of treating said silicon dioxide composition with fluid H O in an amount and at a temperature sufficient to remove essentially all of the halogen from'said silicon dioxide composition without fusing the same.

4. The method according to claim 3 in which said fluid H O is steam.

5. The method according to claim 1 in which said halogen gas contains additionally an oxidizing gas in an amount up to below 66% by volume of the total volume of said halogen and oxidizing gases.

6. The method according to claim 5 containing the additional step of treating said silicon dioxide composition with fluid H O at a temperature and in an amount sufficient to remove essentially all of the halogen contained in said silicon dioxide composition without fusing the same.

7. The method according to claim 6 in which said fl i B 0 is steam.

' 8. The method which comprises treating a brown, particulate, substantially fibrous, disproportionated solid se" lected from the group consisting of silicon monoxide and silicon monoxide having from about 1 to 8% by weight of bound nitrogen at'a temperature of from about 700 to about 900 C. with chlorine gas in an amount suflicient to react with at least a portion of the silicon in said solid to form substantially gaseous silicon tetrachloride and to leave a light colored to White, solid, particulate, substantially fibrous silicon dioxide composition containing chlorine in an amount not in excess of about 3% by Weight.

9. The method according to claim 8 containing the additional step of treating said silicon dioxide composition with steam at a temperature below the fusing point of said silicon dioxide composition and in an amount sufficient to remove essentially all of the chlorine contained in said silicon dioxide composition. p

10. The method according to claim 9 in which said steamed silicon dioxide composition containing bound nitrogen from said nitrogen containing silicon monoxide is treated with additional steam in an amount sufficient and at a temperature below the fusing point of said silicon dioxide composition to remove at least a substantial amount of said nitrogen from said silicon dioxide composition.

II. The method according to claim 8 in which said chlorine gas contains additionally up to about 50% by volume of oxygen gas based on the total volume of said chlorine and oxygen gases.

12. The method according to claim 11 containing the additional step of treating said silicon dioxide composition .with steam at a temperature below the fusing point of said silicon dioxide composition and in an amount suflicient to remove essentially all of the chlorine contained in said silicon dioxide composition.

13. The method according to claim 12 in which said steamed silicon dioxide composition containing bound nitrogen from said nitrogen containing silicon monoxide is treated with steam in an additional amount and at a temperature sufficient to remove essentially all of said bound nitrogen from said silicon dioxide composition without fusing the same.

' 14. A composition characterized by being light colored to white in color, particulate, and solid and comprising silicon dioxide substantially free of metallic impurities and containing halogen attached to the silicon of said silicon dioxide in an amount not in excess of about 3% by weight.

15. A composition characterized by being particulate, substantially free of metallic impurities, light colored to white and solid and being selected from the group consisting of silica and silica containing bound nitrogen groups, the number of atoms of nitrogen in said nitrogen groups being substantially equivalent to the number of nitrogen atoms in particulate, solid silicon monoxide containing from about 1 to 8% by weight of bound nitrogen and said particulate, light colored to white solid containing halogen attached to the silicon of said particulate, light colored to white solid and being present in an amount not in excess of about 3% by weight.

16. A composition according to claim 15 in which said halogen is chlorine.

17. A composition according to claim 15 characterized further by being substantially fibrous.

18. A composition according to claim 17 in which said halogen is chlorine.

19. A composition according to claim 17 in which said particulate, light colored to white solid has been treated with fluid H O in an amount and at a temperature sufficient to remove essentially all of said halogen from and without fusing said particulate, light colored to white solid.

20. A composition according to claim 18 in which the fibers of said substantially fibrous composition have a ratio of length to width of at least about 10:1 to 50:1,

migron and ha'ye aslirface areaof at least about 6 0, to

200' s'qii eime t pe a n- 21 A. compositiomaccording,to claim 18 in which. said particulatqtlight colored to white solidvhas been treated with fluid H qin an amount, and ate. temperature sufficient to: remoye essentially .all of said chlorine from and w hsmt u n fi partic late,. .lig ,t; o o e to ,white,

solid.

22, A- composition according to claim i 21 ,in which the 3. esmethqd w ch c mp se t eat ng a solid 17. prising silicon monoxide at a temperature of from about halogenwgesjn an amount sufiicient to react with atleast a portion of the silicon in said solid to form gaseous:

silicon halides and to leave solid silicon dioxide containinghalogen-in' an amount not in excess of about 3% by weight;-

ReferencesiCitedin the file: of ithiS patent 1 UNITED STATES-PATENTS 1,806,690 Kroner et a1 May 26, 1931 2,504,357 Swallen Apr. 18,1950 2,535,036 Bronghtom Dec, 26,- 1950 2578605 Sears Dec; 11, 1951 2;657','149' Iler Oct. 27, 1953 FOREIGN PATENTS 12,209" Great Britain .-.-t-t--.-.-E.- v 1906 254,726 Great Britain July 28, 1927 UNITED STATES PATENT OFFICE December 23 1958 Roger Wc Strass'burg after "does" insert In not ==-=a Signed and sealed this 2nd day of June 1959 SEAL) Attest:

KARL Ha AXLINE ROBERT C. WATSON Attesting Officer Commissioner of Patents Qolumn 4, line 68, V 

1. THE METHOD WHICH COMPRISES TREATING A BROWN, PARTICULATE, DISPROPORTIONATED SOLID SELECTED FROM THE GROUP TAINING FROM ABOUT 1 TO 8% BY WEIGHT OF BOUND NITROGEN TAINING FROM ABOUT 1 TO 8% BY WEIGHT OF BOUND NITROGEN AT A TEMPERATURE OF FROM ABOUT 600*C. TO BELOW THE FUSION POINT OF SAID SOLID WITH A HALOGEN GAS IN AN AMOUNT SUFFICIENT TO REACT WITH AT LEAST A PORTION OF THE SILICON IN SAID SOLID TO FORM GASEOUS SILICON HALIDES AND TO LEAVE A LIGHT COLORED TO WHITE, SOLID, PARTICULATE, SILICON DIOXIDE COMPOSITION CONTAINING HALOGEN IN AN AMOUNT NOT IN EXCESS OF ABOUT 3% BY WEIGHT.
 3. THE METHOD ACCORDING TO CLAIM 1 CONTAINING THE ADDITIONAL STEP OF TREATING SAID SILICON DIOXIDE COMPOSITION WITH FLUID H2O IN AN AMOUNT AND AT A TEMPERATURE SUFFICIENT TO REMOVE ESSENTIALLY ALL OF THE HALOGEN FROM SAID SILICON DIOXIDE COMPOSITION WITHOUT FUSING THE SAME. 